Bosch targets 50% smaller power electronics for hybrids

Packaging progress: Bosch's compact power electronics unit used on the 2011 VW and Porsche HEVs is 33% smaller than previous units, company engineers claim.

Packaging progress: Bosch's compact power electronics unit used on the 2011 VW and Porsche HEVs is 33% smaller than previous units, company engineers claim.

Bosch's integrated motor generator on the VW and Porsche hybrid SUVs is positioned between the ICE and eight-speed transmission.

While the automotive industry remains fixated on 3.0-L cars (3.0 L meaning fuel consumption of 3.0 L/100 km), Bosch is focusing on 5.0 liters—which describes the package-volume target for a power electronics unit developed by the company for a production parallel-hybrid vehicle.

Bosch's power electronics unit in the 2011 Porsche Cayenne S and Volkswagen Touareg parallel hybrids consumes 10 L of package volume, which itself is 33% smaller than previous units, company engineers claim. It has done so without compromising performance.

“Our aim is to get the next-generation version down to 5.0 liters,” said Matthias Küsell, Bosch’s Head of Development and Customer Projects, Hybrid and Electric Vehicles. The power electronics, which include an inverter, are a core component that provide an interface between the vehicle's high-voltage electric drive and its 12-V electrical system.

For the new Porsche and VW models, Bosch supplies the power electronics, electric motor, and the Motronic control unit. The Motronic ECU governs actuation of the electric motor, the gasoline engine, or the two in parallel. Bosch also supplies an integrated motor generator (IMG).

Both Porsche and VW hybrids can cruise at 50-60 km/h (31-37 mph) on electric power only, the companies claim. A Sanyo 288-V nickel-metal hydride (NiMH) battery with a capacity of 1.7 kW·h is fitted.

Bosch states that lifting off the accelerator pedal at speeds up to about 160 km/h (99 mph) activates “sailing mode”—the ICE shuts down while all necessary systems are maintained. When braking, the hybrid control unit monitors brake pedal pressure to decide what braking torque should be electrically set by the IMG; ABS and electronic stability program (ESP) always take precedent.

As usual with hybrid vehicles, Bosch faced the need to achieve acceptably smooth transition between electric, hybrid, and ICE power. To do so, the control unit receives data from the ICE, electric motor, battery, clutch, and other components, explained Küsell.

The unit uses the data flow to analyze and control powertrain interaction, with an adaptive clutch operating to smooth transitions. Its ability to ensure electric motor and ICE are turning at the same speed when transferring torque is a core aspect of parallel-hybrid technology.

An additional CAN bus interface is used to exchange data with relevant hybrid components, including the rate of individual injections of fuel.

Development of advanced automotive technologies is increasingly being driven by suppliers, rather than OEMs. And megadeals worth at least $500 million that are behind a growing number of next-gen technologies may reach the highest level since before the Great Recession. That’s the view from Las Vegas, as the 2017 CES (formerly the Consumer Electronics Show) opens to over 160,000 attendees.